1. Field of the Invention
The present invention relates to a solar cell module having an improved reliability against folding. More particularly, the present invention relates to a highly reliable solar cell module which excels in flexibility and has good exterior appearance and which can be freely bent and can be used as a building material such as a roofing material.
2. Related Background Art
There have been proposed a variety of so-called roof-integral type solar cell modules capable for use as a roofing material of a building by integration with other roofing materials. These solar cell modules are usually produced in a manner of electrically connecting a plurality of solar cells with each other in series connection by an electrically conductive connection material into a cell block comprising the solar cells integrated in series connection, sealing said cell block on a reinforcing member using a sealing resin into a module, and bending the reinforcing member of the module as desired.
For instance, Japanese Unexamined Patent Publication No.302924/1995 (hereinafter referred to as Japanese document '924) discloses a roof-integral type solar cell module shaped in a plate-like form which can be provided at a reasonable cost on the market for the following reasons. This solar cell module has good compatibility with ordinary roofing material, and it can be readily installed by way of ordinary roofing work where hanging tools and the like used in ordinary roofing work can be used. In addition, the solar cell module can be readily processed into an appropriate roof-shaped solar cell module by means of a roll former making machine without using extra instruments.
In Japanese document '924, there is described a roof-integral type solar cell module processed by way of forming using a roll former making machine to have a shape suitable for crosswise roofing. The solar cells in this solar cell module are arranged in a flat area of the module so as to prevent them from suffering from stress upon the forming treatment and the like. Particularly, this solar cell module shaped suitable for crosswise roofing comprises a flat portion having the solar cells arranged therein, a solar cell-free ridge side meshing portion and a solar cell-free eaves side meshing portion, wherein the ridge side meshing portion and the eaves side meshing portion function as fixing means when the solar cell module is installed.
Now, for the configuration for a solar cell module used as a roofing material, there are known a roll-like configuration, a roof tile-like configuration, a flat configuration, and the like.
Recently, there is a demand on the market for providing a solar cell module having a curved configuration such as a corrugated configuration which is usable as a roofing material.
Besides, there is also a demand on the market for providing a solar cell module having no reinforcing member and which can be freely bent.
In the case of a conventional solar cell module in which a plurality of solar cell modules integrated in series connection by means of an electrically conductive connection material are held on a reinforcing member while being sealed by a sealing resin, when the solar cell module is bent into a desired shape, a problem is likely to occur in that the electrically conductive connection material cracks because it is difficult to bend.
FIG. 14 is a schematic cross-sectional view illustrating the constitution of an example of such a conventional solar cell module.
The solar cell module shown in FIG. 14 comprises a cell block comprising a plurality of solar cells 1402 electrically connected with each other by an electrically conductive connection material 1405 and which is sealed by a resin filler material 1403 on a reinforcing member 1401 while covering a front side of the cell block by a surface protective film 1404. The solar cell module shown in FIG. 14 has a curved shape formed by bending the reinforcing member 1401.
In the following, description will be made of a stress caused at a bent portion in the solar cell module when the reinforcing member 1401 is bent.
Corrugation of the solar cell module as shown in FIG. 14 is conducted by bending the reinforcing member 1401. In bending the reinforcing member 1401 in this case, a neutral line 1410 of the reinforcing member 1401 is engaged in the bending as a processing neutral line. Because of this, a portion of the sealed area having a radius of curvature which is smaller than that of the processing neutral line 1410 suffers from a shrinkage force. Particularly, the solar cell 1402 or the electrically conductive connection material 1405 situated in a recessed portion suffers from a shrinkage force to deform. Similarly, the solar cell 1402 or the electrically conductive connection material 1405 situated in a portion of the sealed area having a radius of curvature which is smaller than that of the processing neutral line 1410 suffers from an extension force to extendedly deform.
In view of this situation, in the case where the solar cell module is subjected to bending treatment using the foregoing roll former making machine, the bending treatment is conducted with due care so that pressure is not applied on the solar cell-bearing portions. However, in the case where the solar cell module is processed to have a corrugated shape as shown in FIG. 14 by way of press working, the solar cell-bearing portions unavoidably suffer from pressure, where such deformation due to the extension or shrinkage as described in the above occurs.
Separately, based on the description of the Japanese document '924, the present inventors prepared a solar cell module having the configuration shown in FIG. 14. Particularly, there was first prepared a solar cell module which comprises a cell block comprising a plurality of solar cells 1402 electrically connected with each other by an electrically conductive connection material 1405 and which is sealed by a resin filler material 1403 on a reinforcing member 1401 while covering a front side of the cell block by a surface protective film 1404. The solar cell module was processed to have such a corrugated shape as shown in FIG. 14.
For the resultant solar cell module, evaluation was conducted. As a result, the solar cell module was not problematic at the beginning stage. But in a weathering test, the solar cell module was found to have such problems as will be described in the following. The electrically conductive connection materials 1405 (which connect the solar cells 1402 in series connection) situated in the recessed and protruded portions of the corrugated shaped and which are curved along the recessed and protruded portions tend to partially separate from the resin filler material 1403 covering the electrically conductive connection materials 1405 due to a difference of curvature R between their inside diameter and their outside diameter, where cracking is likely to occur at the electrically conductive connection materials 1405.
By the way, in the case of a solar cell module which is not provided with a reinforcing member, it is necessary that its power outputting terminals be sufficiently flexible and highly reliable.